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Idea Transcript
Titration Curve weak acid with strong base overshoot This region is calculated simply by determining the amount of OHin EXCESS that has been added. No equilibrium calculations necessary.
pH pH = 7.00
buffer zone a “type 2” calculation conjugate ratios are known, use Henderson-Hasselbach to calculate pH.
pH = 7.00 The equivalence point (endpoint) is the same as a regular (type 1) salt of a weak acid problem (NaA). You know [A-] and you can calculate pH. Also note that the pH must be greater than 7 due to the hydrolysis of A-. A- + H2O
HA +
OH-
mL of base The START of the titration is the same as a regular (type 1) weak acid problem. You know Ka and [HA] so you can calculate pH. HA
H+
+
A-
The half-way point is important! After you have determined the equivalence point (endpoint) of the titration, go to half that value. The pH at the half-titration point is equal to the pKa of the weak acid. pH = pKa